Mold side action

Number of cavities, layout and size of cavities/runners/gates/cooling lines/side actions/knockout pins/etc. Relate layout to maximize proper performance of melt and cooling flow patterns to meet part performance requirements preengineer design to minimize wear and deformation of mold (use proper steels) lay out cooling lines to meet temperature to time cooling rate of plastics (particularly crystalline types). 

GmbH). A center mold plate separates the two processes and is supported by guide arms on the debars. During processing a robot loads a metal blank into the hydroform section and moves the shaped blank from the previous cycle to the IM side. The molds closing action drives the hydro-forming process, and the already shaped blank is overmolded with plastics. 

Different actions in molds occur such as using ejector pins to remove molded parts from their cavities. Side actions of molds may be required to remove parts that have undercuts. Other actions may be required such as unscrewing threaded parts, including inserts, and so on (Chapter 17). 

Figure 5.84 Examples of simplifying mold construction to produce openings without side action movements.

Lines left on a molded part by poor mating and fit of side action cores. 

Machining is also used in combination with other processes. Some processes require that gates be removed or parts trimmed by mechanical means before they are ready to be used. Machining may be used to create details the process cannot create. An example of this type of application would be holes in thermoformed parts. Finally, machining may be used because the product s production volume is too low to warrant the additional tooling cost necessary to mold the detail into the part. An example of this type of application would be a hole in an injection-molded part parallel to the parting line that would require an expensive side action. The additional amortization cost could exceed the cost of drilling the hole for low volumes. 

Note in this illustration that there is a hole in the side of the part. The core that makes that hole would interfere with the ejection of the part from the mold. Therefore, that core is placed in a removable section which has to be replaced after every cycle. This procedure is too time consuming for high-speed production, and mechanical devices, such as air cylinders and cams, which are activated by the relative motion between the two mold halves, are used to achieve higher production rates. These mechanisms are referred to as slides or side actions and they can also be used to operate the halves of a split cavity when it is used for injection molding. 

Flash specification. Flash consists of small amounts of plastic which adhere to a molded part beyond its desired contour, usually where wear occurs like the fitments around side actions, ejector pins, and at the parting line. In small amounts, it can be removed with a variety of cutting and scraping devices ranging from clippers to a tile knife. For large amounts, typical of compression-molded parts, a router is used. 

It is possible to strip undercuts for parts molded of these processes in some cases and threads can be molded-in. However, side actions or split cavities, as would be required for details A and G, are more commonplace. Threaded inserts, like those at E and H, can also be molded-in. However, it may be more advantageous to emplace them after molding with adhesives since the molding cycle will be shorter and the risk of one misplaced insert ruining an entire moldment is ehminated. The other common methods of assembling compression, transfer, and thermoset injection-molded parts are self-tapping screws (holes can be tapped), adhesives, snap-fits, press-fits, and the usual screw and bolt techniques. None of the plastics welding techniques can be used with thermoset parts. 

Injection molding is capable of accommodating the broadest range of materials. Nearly all the thermoplastics can be injection molded and, with special equipment, even many thermoset materials can be used. The mold capabilities of the process are also a major asset. Moldmakers have succeeded in constructing incredibly complex molds using side actions to create holes perpendicular to the parting line, split cavities for imusual shapes, and cores which collapse to permit withdrawal from undercuts. 

The bottom-plug insert forms the bottom or push-up area of the container in some molds, this insert must be retractable. Generally, the push-up of polyolefin bottles can be stripped without side action if the height is less than 5 mm. With rigid resins, this height is reduced to 0.8 mm. When side action is required, an air cylinder, cam, or spring mechanism is used. 

Snap fits usually require undercuts, so a mold with a side action is usually used, as shown in Figure 5-44 [2, 11]. Another approach when an opening at the base of the flexing finger is permitted is shown in Figure 5-45 [2, 11]. There are times when all that has to be done is just pop it off the mold, taking advantage of the plastic s flexibility. Another type of system is the snap-on or snap-in kind, used primarily in round parts (see Fig. 5-46) [2]. 

The term coring in injection molding refers to the addition of steel to the mold for the purpose of eliminating plastic material in that area. Usually, coring is necessary to create a pocket or opening in the part, or simply for the purpose of reducing an overly heavy wall section (see Fig. 11-64). For simplicity and economy in injection molds, cores should be parallel to the line of draw of the mold. Cores placed in any other direction usually create the need for some type of side action (either a cam or hydraulic cylinder) or manually loaded and unloaded loose cores [2]. 

The mold opens, leaving the molding attached by shrinkage to the core. During opening, the side action is retracted by a cam to release an undercut on the molding. 

Every modification in design, as well as remedial actions, must be made after due consideration of building physics. Otherwise negative side effects can occur. Examples are locally high relative humidity in air, condensation of moisture and development of mold. With due consideration to the constraints laid by building physics, however, modifications to radon safe design can give positive tradeoffs as reduced possibility for moisture transport and development of mold. 

Pressure deeay during the molding ean be a serious problem in billets that are taller than 100 mm. This can be corrected by pressurizing the resin from both sides if a double action press is available. 

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